LED package having an array of light emitting cells coupled in series

ABSTRACT

Disclosed is a light emitting diode (LED) package having an array of light emitting cells coupled in series. The LED package comprises a package body and an LED chip mounted on the package body. The LED chip has an array of light emitting cells coupled in series. Since the LED chip having the array of light emitting cells coupled in series is mounted on the LED package, it can be driven directly using an AC power source.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.11/908,112 filed Sep. 7, 2007, which is a U.S. national stageapplication of PCT International Application No. PCT/KR2005/003565,filed on Oct. 26, 2005, and claims priority from and the benefit ofKorean Patent Application No. 10-2005-0026090, filed on Mar. 29, 2005;Korean Patent Application No. 10-2005-026078, filed on Mar. 29, 2005,Korean Patent Application No. 10-2005-0026067, filed Mar. 29, 2005;Korean Patent Application No. 10-2005-0026108, filed Mar. 29, 2005; andKorean Patent Application No. 10-2005-0020377, filed Mar. 11, 2005 whichare hereby incorporated by reference for all purposes as if fully setforth herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a light emitting diode (LED) package,and more particularly, to an LED package having an array of lightemitting cells coupled in series, which can be directly connected to anddriven by an AC power source.

2. Discussion of the Background

Since light emitting diodes (LEDs) can realize colors, they have beenwidely used for indicating lamps, electric display boards and displays.The LEDs have also been used for general illumination because they canrealize white light. Since such LEDs have high efficiency and longerlife span and are environment-friendly, their applicable fields havebeen continuously expanded.

Meanwhile, an LED is a semiconductor device which is formed of a p-njunction structure of semiconductors and emits light throughrecombination of electrons and holes. In general, the LED is driven by acurrent flowing in a direction. Thus, when the LED is driven using an ACpower source, there is a need for an AC/DC converter for converting anAC current to a DC current. With the use of an AC/DC converter togetherwith LEDs, installation costs of LEDs increase, which makes it difficultto use the LEDs for general illumination at home. Therefore, to use LEDsfor general illumination, there is a need for an LED package capable ofbeing directly driven using an AC power source without an AC/DCconverter.

Such an LED lamp is disclosed in U.S. Pat. No. 5,463,280 entitled “LIGHTEMITTING DIODE RETROFIT LAMP” issued to James C. Johnson. The LED lampincludes a plurality of light emitting diodes coupled in series, a meansfor limiting a current, and a diode bridge. Since an AC current isconverted to a DC current through the diode bridge, the LED lamp can bedriven by an AC power source.

However, since the LED lamp have serially coupled LEDs with individualLED chips mounted thereon, the process of coupling the LEDs iscomplicated, and the size of the LED is lamp considerably increasessince the LEDs occupy a large space.

In the meantime, since the luminous power of an LED is substantially inproportion to an input power, increase of electric power to be inputinto the LED enables high luminous power. However, the junctiontemperature of the LED increases due to the increase of the inputelectric power. The increase of the junction temperature of the LEDresults in decrease of photometric efficiency that represents the degreeof conversion of input energy into visual light. Therefore, it isnecessary to prevent the junction temperature of the LED from rising dueto the increased input power.

An object of the present invention is to provide a light emitting diode(LED) package, which can be driven using an AC power source without anexternal AC/DC converter and thus can be miniaturized.

Another object of the present invention is to provide an LED package ofwhich fabricating processes can be simplified and which is advantageousto mass production.

A further object of the present invention is to provide an LED package,which can improve photometric efficiency by easily dissipating generatedheat and has a stable structure.

SUMMARY OF THE INVENTION

In order to achieve these objects of the present invention, the presentinvention provides an LED package having an array of light emittingcells coupled in series. An LED package according to an aspect of thepresent invention comprises a package body, and an LED chip mounted onthe package body. The LED chip has an array of light emitting cellscoupled in series. Since the LED package according to this aspect of thepresent invention mounts the LED chip having the array of light emittingcells coupled in series thereon, it can be driven directly is using anAC power source.

Here, the term “light emitting cell” means a minute LED formed in asingle LED chip. Although an LED chip generally has only one LED, theLED chip of the present invention has a plurality of light emittingcells.

In embodiments of the present invention, the LED chip comprises asubstrate and a plurality of light emitting cells formed on thesubstrate. The light emitting cells are electrically insulated from thesubstrate.

In some embodiments of the present invention, the LED chip may comprisewires for electrically connecting the light emitting cells to oneanother in series. The array of light emitting cells coupled in seriesis formed by the light emitting cells and the wires.

In other embodiments of the present invention, a submount may beinterposed between the LED chip and the package body. The submount mayhave electrode patterns corresponding to the light emitting cells, andthe electrode patterns may couple the light emitting cells to oneanother in series. As a result, the array of light emitting cellscoupled in series is formed by the light emitting cells and theelectrode patterns.

Further, the LED chip may further comprise a rectification bridge unitfor applying predetermined rectified power to the array of lightemitting cells coupled in series. Accordingly, the LED chip can bedriven using an AC power source.

Meanwhile, the LED chip may further comprise one or more arrays of lightemitting cells coupled in series. The arrays of light emitting cellscoupled in series may be connected to one another in reverse parallel.Accordingly, the LED chip can be driven using an AC power source withouta rectification bridge unit or an AC/DC converter.

An encapsulant and/or a molding member may encapsulate the LED chip. Theencapsulant and/or molding member protect the LED chip against moistureor external forces. The terms “encapsulant” and “molding member” hereinare used without any differences from each other. However, in someembodiments, they are used together for discriminately referring tocomponents.

Meanwhile, the LED package may further comprise a phosphor forconverting the wavelength of light emitted from the LED chip. Thephosphor may be incorporated in the molding member, or it may be locatedbetween the molding member and the LED chip, or on the molding member.With appropriate selection of the phosphor, it is possible to provide aLED package that can realize light with various colors or white light.

Meanwhile, the package body may have various structures.

For example, the package body may be a printed circuit board (PCB) withlead electrodes. The LED chip is electrically connected to the leadelectrodes. In addition thereto, a reflective portion may be located onthe PCB to reflect light emitted from the LED chip and incident thereon.

Moreover, the LED package may further comprise a pair of lead framesspaced apart from each other, and a heat sink. The package body supportsthe pair of lead frames and the heat sink. The package body may have anopening for exposing a portion of each of the lead frames and an upperportion of the heat sink. Meanwhile, the LED chip is mounted on the heatsink. By employing the heat sink, heat generated from the LED chip canbe easily dissipated.

In some embodiments of the present invention, the heat sink may beconnected directly to one of the lead frames at a side surface thereofand spaced apart from the other of the lead frames. Accordingly, theheat sink can be prevented from being separated from a package body,thereby providing an LED package that is stable in view of itsstructure.

In addition thereto, the heat sink may comprise a base and a protrusionprotruding is upwardly at a central portion of the base. Accordingly,the area of a heat dissipation surface increases so that heat can beeasily dissipated and the size of an LED package can be minimized aswell. The protrusion may protrude beyond a top surface of the packagebody.

Further, the heat sink may have a lead frame-receiving groove forreceiving one of the lead frames at a side surface of the protrusion.The directly connected lead frame may be inserted into the leadframe-receiving groove. On the contrary, the heat sink and the leadframe connected directly to the heat sink may be formed integrally witheach other.

In other embodiments of the present invention, the package body has athrough-hole exposed through the opening. Further, the pair of leadframes have a pair of inner frames exposed inside the opening of thepackage body, and outer frames extending from the respective innerframes and protruding to the outside of the package body. In additionthereto, the heat sink is combined with a lower portion of the packagebody through the through-hole.

In addition, the heat sink may comprise a base combined with the lowerportion of the package body, and a protrusion protruding upwardly at acentral portion of the base and coupled with the through-hole. Further,the heat sink may have a latching step at a side surface of theprotrusion. The latching step is caught by an upper surface of thepackage body or inserted into a sidewall defining the through-hole sothat the heat sink is prevented from being separated from the packagebody.

According to another aspect of the present invention, there is providedan LED lamp on which an LED chip with an array of light emitting cellscoupled in series is mounted. The LED lamp comprises a first lead havinga top portion and a pin-type or snap-type leg extending from the topportion, and a second lead arranged to be spaced apart from the firstlead and having a pin-type or snap-type leg corresponding to the firstlead. The LED chip with the array of light emitting cells coupled inseries is mounted on the top portion. Meanwhile, bonding wireselectrically connect the LED chip to the first lead and the second lead,respectively. In addition, a molding member encapsulates the top portionof the first lead, the LED chip and a portion of the second lead.According to this aspect, by mounting the LED chip with the array oflight emitting cells coupled in series, it is possible to provide an LEDlamp that can be driven using an AC power source without an AC/DCconverter.

The top portion of the first lead may have a cavity, and the LED chipmay be mounted inside the cavity.

Meanwhile, if the first and second leads have pin-type legs, each of thefirst and second leads may have two pin-type legs. Such an LED lamp isgenerally known as a high flux LED lamp. Thus, according to this aspect,it is possible to provide a high flux LED lamp which can be driven usingan AC power source.

Furthermore, a heat sink may extend from the top portion of the firstlead in parallel with the leg of the first lead. The heat sink easilydissipates heat generated from the LED chip, thereby improving thephotometric efficiency of the LED lamp. Further, the heat sink may havegrooves on the surface thereof. The grooves increase the surface area ofthe heat sink, thereby more enhancing heat dissipation performance.

In embodiments of this aspect, the LED chip comprises a substrate and aplurality of light emitting cells formed on the substrate. The lightemitting cells are electrically insulated from the substrate.

In some embodiments of this aspect, the LED chip may comprise wires forconnecting the light emitting cells to one another in series.

In other embodiments of this aspect, a submount may be interposedbetween the LED chip and the top portion. The submount may haveelectrode patterns corresponding to the light emitting cells, and theelectrode patterns may connect light emitting cells to one another inseries.

Meanwhile, the LED chip may further comprises a rectification bridgeunit for applying predetermined rectified power to the array of lightemitting cells coupled in series.

Further, the LED chip may further comprise one or more arrays of lightemitting cells coupled in series. The arrays of light emitting cellscoupled in series may be connected to one another in reverse parallel.

Meanwhile, the LED lamp may further comprise a phosphor for convertingthe wavelength of light emitted from the LED chip. The phosphor may bedispersed in the molding member, or may be located between the moldingmember and the LED chip or on the molding member.

According to a further aspect of the present invention, there isprovided an LED package having light emitting cells coupled in series.The LED package comprises a package body. A submount with electrodepatterns is mounted on the package body. Meanwhile, the light emittingcells are bonded to the electrode patterns of the submount. At thistime, the light emitting cells are coupled to one another in seriesthrough the electrode patterns. In addition thereto, a molding membermay encapsulate the light emitting cells.

The package body may be a printed circuit board with lead electrodes,and the submount may be electrically connected to the lead electrodes.

Meanwhile, the LED package according to this aspect may further comprisea pair of lead frames spaced apart from each other, and a heat sink. Thepackage body supports the pair of lead frames and the heat sink, and itmay have an opening for exposing a portion of each of is the lead framesand an upper portion of the heat sink. Further, the submount may bemounted on the heat sink.

According to a still further aspect of the present invention, there isprovided an LED lamp having an array of light emitting cells coupled inseries. The LED lamp comprises a first lead having a top portion and apin-type or snap-type leg extending from the top portion, and a secondlead arranged to be spaced apart from the first lead and having apin-type or snap-type leg corresponding to the first lead. Meanwhile, asubmount with electrode patterns is mounted on the top portion. Inaddition thereto, the light emitting cells are bonded to the electrodepatterns of the submount. At this time, the light emitting cells arecoupled to one another in series through the electrode patterns.Further, bonding wires electrically connect the submount to the firstand second leads, respectively. Meanwhile, a molding member encapsulatesthe top portion of the first lead, the light emitting cells and aportion of the second lead.

According to the present invention, it is possible to provide an LEDpackage and an LED lamp, which can be driven using an AC power sourcewithout an external AC/DC converter and thus can be miniaturized.Further, since light emitting cells formed on a single substrate areemployed, the process of fabricating a package can be simplified andthus is advantageous to mass production. Moreover, since generated heatcan be easily dissipated by employing the heat sink, the photometricefficiency of the light emitting cells can be improved. Furthermore,since the heat sink can be prevented from being separated from thepackage body, it is possible to provide an LED package that is stable inview of its structure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 2 are sectional views illustrating light emitting diode(LED) chips is each of which has an array of light emitting cellscoupled in series, which are applicable to embodiments of the presentinvention.

FIGS. 3 to 5 are sectional views illustrating arrays of light emittingcells coupled in series through electrode patterns of a submount, whichare applicable to embodiments of the present invention.

FIGS. 6 and 7 are circuit diagrams illustrating arrays of light emittingcells according to embodiments of the present invention.

FIGS. 8 to 10 are sectional views illustrating LED packages according toembodiments of the present invention.

FIG. 11 is a sectional view illustrating an LED package on which aplurality of light emitting devices with an array of light emittingcells coupled in series are mounted.

FIGS. 12 and 13 are sectional views illustrating LED packages each ofwhich employs a heat sink, according to some embodiments of the presentinvention.

FIGS. 14 to 18 are views illustrating LED packages each of which employsa heat sink, according to other embodiments of the present invention.

FIGS. 19 to 23 are views illustrating LED packages each of which employsa heat sink, according to further embodiments of the present invention.

FIG. 24 is a sectional view illustrating an LED lamp having lightemitting cells coupled in series according to an embodiment of thepresent invention.

FIGS. 25 to 32 are views illustrating high flux LED lamps according toother embodiments of the present invention.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Hereinafter, preferred embodiments of the present invention will bedescribed in is detail with reference to the accompanying drawings. Thefollowing embodiments are provided only for illustrative purposes sothat those skilled in the art can fully understand the spirit of thepresent invention. Therefore, the present invention is not limited tothe following embodiments but may be implemented in other forms. In thedrawings, the widths, lengths, thicknesses and the like of elements areexaggerated for convenience of illustration. Like reference numeralsindicate like elements throughout the specification and drawings.

<Array of Light Emitting Cells Coupled in Series>

A light emitting diode (LED) package according to the present inventionincludes an array of light emitting cells coupled in series. FIGS. 1 to5 are sectional views illustrating arrays of light emitting cellscoupled in series, which are applicable to embodiments of the presentinvention. Here, FIGS. 1 and 2 are sectional views illustrating LEDchips each of which has an array of light emitting cells coupled inseries through wires, FIGS. 3 and 5 are sectional views illustrating LEDchips each of which has an array of light emitting cells coupled inseries through electrode patterns of a submount, and FIG. 4 is asectional view illustrating an array of light emitting cells coupled inseries through electrode patterns of a submount.

Referring to FIGS. 1 and 2, an LED chip of the present invention isformed on a substrate 20 and has a plurality of light emitting cells100-1 to 100-n coupled to one another in series through wires 80-1 to80-n. That is, the LED chip comprises the plurality of light emittingcells 100 in which N-type semiconductor layers 40 and P-typesemiconductor layers 60 of the adjacent light emitting cells 100-1 to100-n are electrically connected, an N-type pad 95 is formed on theN-type semiconductor layer 40 of a light emitting cell 100-n located atone end of the LED chip, and a P-type pad 90 is formed on the P-typesemiconductor layer 60 of a light emitting cell 100-1 located at theother end thereof.

The N-type semiconductor layers 40 and the P-type semiconductor layers60 of is the adjacent light emitting cells 100-1 to 100-n areelectrically connected to each other through the metal wires 80 to forman array of the light emitting cells coupled in series. The lightemitting cells 100-1 to 100-n can be coupled in series as many as thenumber of light emitting cells that can be driven by an AC power source.In the present invention, the number of the light emitting cells 100coupled in series is selected according to a voltage/current for drivinga single light emitting cell 100 and an AC driving voltage applied to anLED chip for illumination.

In the LED chip with first to n-th light emitting cells 100-1 to 100-ncoupled in series, as shown in FIG. 1, the P-type pad 90 is formed onthe P-type semiconductor layer 60 of the first light emitting cell100-1, and the N-type semiconductor layer 40 of the first light emittingcell 100-1 and the P-type semiconductor layer 60 of the second lightemitting cell 100-2 are connected through a first wire 80-1. Further,the N-type semiconductor layer 40 of the second light emitting cell100-2 and the P-type semiconductor layer (not shown) of the third lightemitting cell (not shown) are connected through a second wire 80-2. AnN-type semiconductor layer (not shown) of the (n−2)-th light emittingcell (not shown) and a P-type semiconductor layer 60 of the (n−1)-thlight emitting cell 100-n−1 are connected through an (n−2)-th wire80-n−2, and an N-type semiconductor layer 40 of the (n−1)-th lightemitting cell 100-n−1 and a P-type semiconductor layer 60 of the n-thlight emitting cell 100-n are connected through an (n−1)-th wire 80-n−1.Further, the N-type pad 95 is formed on the N-type semiconductor layer40 of the n-th light emitting cell 100-n.

The substrate 20 in the present invention may be a substrate on which aplurality of LED chips can be fabricated. Here, positions designated by“A” as shown in FIGS. 1 and 2 refer to cutting positions for cutting thesubstrate into discrete LED chips.

Further, the aforementioned LED chip may have rectification diode cellsfor is rectifying an external AC voltage. The diode cells are connectedin the form of a rectification bridge to form a bridge rectifier. Thebridge rectifier is arranged between an external power source and thearray of light emitting cells coupled in series. Accordingly, a currentflowing in a certain direction is supplied to the array of lightemitting cells coupled in series. The rectification diode cells may havethe same structures as those of the light emitting cells. In otherwords, the rectification diode cells may be formed through the sameprocess as the light emitting cells.

Meanwhile, at least two arrays of light emitting cells coupled in seriesmay be formed on the substrate. The arrays may be connected in reverseparallel to each other to be alternately driven by an AC power source.

A method of fabricating an LED chip having the light emitting cellscoupled in series will be described below.

A buffer layer 30, an N-type semiconductor layer 40, an active layer 50and a P-type semiconductor layer 60 are sequentially grown on asubstrate 20. A transparent electrode layer 70 may further be formed onthe P-type semiconductor layer 60. The substrate 20 may be a substratemade of sapphire (Al₂O₃), silicon carbide (SiC), zinc oxide (ZnO),silicon (Si), gallium arsenide (GaAs), gallium phosphide (GaP),lithium-alumina (LiAl₂O₃), boron nitride (BN), aluminum nitride (AlN) orgallium nitride (GaN), and the substrate 20 may be selected depending onthe material of a semiconductor layer formed thereon. The substrate 20may be a sapphire substrate or a silicon carbide (SiC) substrate in acase where a GaN based semiconductor layer is formed thereon.

The buffer layer 30 is a layer for reducing the lattice mismatch betweenthe substrate 20 and the subsequent layers upon growth of crystals, andmay be, for example, a GaN film. It is preferred that the buffer layer30 is formed of an insulating layer in a case where a SiC substrate is aconductive substrate, and it may be formed of a semi-insulating GaN. TheN-type semiconductor layer 40 is a layer in which electrons are producedand may be formed of an N-type compound semiconductor layer and anN-type cladding layer. At this time, the N-type compound semiconductorlayer may be made of GaN doped with N-type impurities. The P-typesemiconductor layer 60 is a layer in which holes are produced and may beformed of a P-type cladding layer and a P-type compound semiconductorlayer. At this time, the P-type compound semiconductor layer may be madeof AlGaN doped with P-type impurities.

The active layer 50 is a region in which a predetermined band gap and aquantum well are formed so that electrons and holes are recombined, andmay include an InGaN layer. Further, the wavelength of emitted light,which is generated due to the recombination of an electron and a hole,varies depending on the kind of a material constituting the active layer50. Therefore, it is preferred that a semiconductor material comprisedin the active layer 50 be controlled depending on a target wavelength.

Thereafter, the P-type semiconductor layer 60 and the active layer 50are patterned such that a portion of the N-type semiconductor layer 40is exposed, using lithographic and etching techniques. Also, the exposedportion of the N-type semiconductor layer 40 is partially removed toelectrically isolate the light emitting cells 100 from each other. Atthis time, as shown in FIG. 1, a top surface of the substrate 20 may beexposed by removing an exposed portion of the buffer layer 30, or theetching may be stopped at the buffer layer 30. In a case where thebuffer layer 30 is conductive, the exposed portion of the buffer layer30 is removed to electrically isolate the light emitting cells.

By using the same process as the aforementioned fabricating process,diode cells is for a rectification bridge may be formed at the sametime. It will be apparent that diode cells for a rectification bridgemay be separately formed through a typical semiconductor fabricatingprocess.

Then, the conductive wires 80-1 to 80-n for electrically connecting theN-type semiconductor layers 40 and the P-type semiconductor layers 60 ofthe adjacent light emitting cells 100-1 to 100-n are formed through apredetermined process such as a bridge process or a step-cover process.The conductive wires 80-1 to 80-n are formed of a conductive materialsuch as metal, silicon doped with impurities, or a silicon compound.

The bridge process is also referred to as an air bridge process, andthis process will be described in brief. First, a photoresist isprovided on a substrate having light emitting cells formed thereon, anda first photoresist pattern having openings for exposing the exposedportion of the N-type semiconductor layer and the electrode layer on theP-type semiconductor layer is then formed using an exposure technique.Thereafter, a metal material layer with a small thickness is formedusing an e-beam evaporation technique or the like. The metal materiallayer is formed on entire top surfaces of the openings and photoresistpattern. Subsequently, a second photoresist pattern for exposing regionsbetween the adjacent light emitting cells to be connected to one anotheras well as the metal material layer on the openings is formed again onthe first photoresist pattern. Thereafter, gold is formed using aplating technique, and the first and second photoresist patterns arethen removed. As a result, wires for connecting the adjacent lightemitting cells to one another are left, and all the other metal materiallayers and photoresist patterns are removed so that the wires canconnect the light emitting cells to one another in the form of bridgesas shown in the figures.

Meanwhile, the step-cover process includes the step of forming aninsulating layer is on a substrate with light emitting cells. Theinsulating layer is patterned using lithographic and etching techniquesto form openings for exposing the N-type semiconductor layer and theelectrode layer on the P-type semiconductor layer. Subsequently, a metallayer for filling the openings and covering the insulating layer isformed using an e-beam evaporation technique or the like. Thereafter,the metal layer is patterned using lithographic and etching techniquesto form wires for connecting the adjacent light emitting cells to oneanother. It is possible to make various modifications to such astep-cover process. Upon use of the step-cover process, the wires aresupported by the insulating layer, thereby improving the reliability ofthe wires.

Meanwhile, the P-type pad 90 and the N-type pad 95 for electricalconnection with the outside are formed on the light emitting cells 100-1and 100-n located at both ends of the LED chip, respectively. Bondingwires (not shown) may be connected to the P-type pad 90 and N-type pad95.

The aforementioned method of fabricating the LED chip of the presentinvention is only a specific embodiment and is not limited thereto.Various modifications and additions can be made thereto depending onfeatures of a device and convenience of a process.

For example, a plurality of vertical light emitting cells each of whichhas an N-type electrode, an N-type semiconductor layer, an active layer,a P-type semiconductor layer and a P-type electrode sequentiallylaminated one above another are formed on a substrate, or light emittingcells having such a structure are arrayed by being bonded on thesubstrate. Then, the plurality of light emitting cells are coupled inseries by connecting the N-type electrodes and P-type electrodes of theadjacent light emitting cells to one another, thereby fabricating an LEDchip. It will be apparent that the vertical light emitting cell is notlimited to the structure of the aforementioned example but may havevarious structures. Further, it is possible to form a is plurality oflight emitting cells on an additional host substrate by forming theplurality of light emitting cells on a substrate, bonding the lightemitting cells on the host substrate, and separating the substrate usinga laser or removing it using a chemical mechanical polishing technique.Thereafter, the adjacent light emitting cells can be coupled in seriesthrough wires.

Each of the light emitting cells 100 comprises the N-type semiconductorlayer 40, the active layer 50 and the P-type semiconductor layer 60,which are sequentially laminated on a substrate 20, and the buffer layer30 is interposed between the substrate 20 and the light emitting cell100. Each of the light emitting cells 100 comprises the transparentelectrode layer 70 formed on the P-type semiconductor layer 60. Further,in case of a vertical light emitting cell, it comprises an N-typeelectrode located beneath the N-type semiconductor layer.

The N-type pad and P-type pad are pads for use in electricallyconnecting the light emitting cell 100 to an external metal wire orbonding wire, and may be formed as a laminated structure of Ti/Au.Further, electrode pads for connection to the wires 80 may be formed onthe P-type and N-type semiconductor layers of the light emitting cells100. In addition, the aforementioned transparent electrode layer 70distributes an input current such that the current is uniformly inputinto the P-type semiconductor layer 60.

The LED chip described with reference to FIGS. 1 and 2 has the array oflight emitting cells 100 coupled in series through the wires 80.However, there are various methods of coupling the light emitting cellsin series. For example, light emitting cells may be coupled in seriesusing a submount. FIGS. 3 to 5 are sectional views illustrating arraysof light emitting cells coupled in series using submounts.

Referring to FIG. 3, an LED chip 1000 has a plurality of flip-chip typelight emitting cells arrayed on a substrate 110. Each of the lightemitting cells comprises an N-type is semiconductor layer 130 formed onthe substrate 110, an active layer 140 formed on a portion of the N-typesemiconductor layer 130 and a P-type semiconductor layer 150 formed onthe active layer 140. Meanwhile, a buffer layer 120 may be interposedbetween the substrate 110 and the light emitting cell. At this time, anadditional P-type electrode layer 160 for reducing the contactresistance of the P-type semiconductor layer 150 may be formed on theP-type semiconductor layer 150. Although the P-type electrode layer maybe a transparent electrode layer, it is not limited thereto. Moreover,the LED chip 1000 further comprises a P-type metal bumper 170 forbumping formed on the P-type electrode layer 150 and an N-type metalbumper 180 for bumping formed on the N-type semiconductor layer 130.Furthermore, a reflective layer (not shown) having a reflectivity of 10to 100% may be formed on the top of the P-type electrode layer 160, andan additional ohmic metal layer for smooth supply of a current may beformed on the P-type semiconductor layer 150.

The substrate 110, the buffer layer 120, the N-type semiconductor layer130, the active layer 140 and the P-type semiconductor layer 150 may beformed of the substrate 20 and the semiconductor layers described withreference to FIGS. 1 and 2.

A submount 2000 comprises a submount substrate 200 having a plurality ofN-regions and P-regions defined thereon, a dielectric film 210 formed onthe surface of the submount substrate 200, and a plurality of electrodepatterns 230 for connecting adjacent N-region and P-region to eachother. Further, the submount 2000 further comprises a P-type bonding pad240 located at an edge of the substrate, and an N-type bonding pad 250located at the other edge thereof.

The N-regions refer to regions to which the N-type metal bumpers 180 inthe LED chip 1000 are connected, and the P-regions refer to regions towhich the P-type metal bumpers 170 in the LED chip 1000 are connected.

At this time, a substrate with superior thermal conductivity is used asthe submount substrate 200. For example, a substrate made of SiC, Si,germanium (Ge), silicon germanium (SiGe), AlN, metal and the like can beused. The dielectric film 210 may be formed as a multi-layered film. Ina case where the substrate is conductive, the dielectric film 210 may beomitted. The dielectric film 210 may be made of silicon oxide(SiO.sub.2), magnesium oxide (MgO) or silicon nitride (SiN).

The electrode pattern 230, the N-type bonding pad 250 and the P-typebonding pad 240 may be made of a metal with superior electricalconductivity.

A method of fabricating a submount substrate for an LED chip havingflip-chip type light emitting cells constructed as above-mentioned willbe described below.

Concave portions and convex portions are formed on the substrate 200 todefine the N-regions and the P-regions thereon. The widths, heights andshapes of the N-regions and P-regions may be modified variouslydepending on the sizes of the N-type metal bumpers 180 and P-type metalbumpers 170 of the LED chip 1000 to be bonded thereon. In thisembodiment, the convex portions of the substrate 200 become theN-regions, and the concave portions of the substrate 200 become theP-regions. The substrate 200 with such a shape may be fabricated using amold or through a predetermined etching process. That is, a mask forexposing the P-regions is formed on the substrate 200, and exposedportions of the substrate 200 are then etched to form the recessedP-regions. Then, the mask is removed so that the recessed P-regions andthe relatively protruding N-regions are formed. Alternatively, therecessed P-regions may be formed by means of machining.

Then, the dielectric film 210 is formed on the entire structure. At thistime, the is dielectric film 210 may not be formed in a case where thesubstrate 200 is not made of a conductive material. If a metal substratewith superior electrical conductivity is used to improve thermalconductivity, the dielectric film 210 is formed to function as asufficient insulator.

The electrode patterns 230 each of which connects adjacent N-region andP-region in pair are formed on the dielectric film 210. The electrodepatterns 230 may be formed through a screen printing method, or theelectrode patterns 230 may be formed by patterning through lithographicand etching techniques after an electrode layer is deposited.

The P-type bumpers 170 of the LED chip 1000 are bonded to the electrodepatterns 230 on the P-regions, and the N-type metal bumpers 180 thereofare bonded to the electrode patterns 230 on the N-regions so that theLED chip 1000 and the submount substrate 200 are bonded together. Atthis time, the light emitting cells of the LED chip 1000 are coupled inseries through the electrode patterns 230 to form an array of lightemitting cells coupled in series. The P-type bonding pad 240 and N-typebonding pad 250 located at both the ends of the array of light emittingcells coupled in series may be connected through bonding wires,respectively.

The metal bumpers 170 and 180, the electrode patterns 230, and thebonding pads 240 and 250 can be bonded through various bonding methods,e.g., a eutectic method using the eutectic temperature.

At this time, the number of the light emitting cells coupled in seriescan be variously modified depending on an electric power source to beused and power consumption of the light emitting cells.

Referring to FIG. 4, the light emitting cells 100 a to 100 c are notarrayed on the substrate (110 in FIG. 3) but are bonded to the submount200 while being separated from one another, as compared with the lightemitting cells of FIG. 3. Such light emitting cells may be formed byseparating the substrate 110 from the LED chip 1000 using a laser or byremoving the substrate 110 using a chemical mechanical polishingtechnique, after bonding the LED chip 1000 on the submount 2000, asshown in FIG. 3. At this time, the N-type metal bumpers 170 and theP-type metal bumpers 180 of adjacent light emitting cells 100 a to 100 care bonded to the electrode patterns 230 formed on the submount 2000 sothat the light emitting cells can be electrically coupled in series.

Referring to FIG. 5, a flat substrate 200 with a plurality of N-regionsand P-regions defined thereon is formed with electrode patterns 230 forconnecting adjacent N-regions A and P-regions B, and an LED chip 1000 isthen mounted on a submount 2000. That is, contrary to FIG. 3, theelectrode patterns 230 are formed on the submount substrate 200 on whichcertain patterns, e.g., concave and convex portions, are not formed, andthe N-type metal bumpers 180 and the P-type metal bumpers 170 ofadjacent light emitting cells of the LED chip 1000 are bonded on theelectrode patterns 230 to electrically connect the light emitting cellsto one another. At this time, it is preferred that the N-type metalbumpers 180 and the P-type metal bumpers 170 be formed such that topsurfaces thereof are located in the substantially same plane.

In these embodiments, although it has been illustrated that the P-typeand N-type metal bumpers 170 and 180 are formed on the light emittingcells within the LED chip 1000, it is not limited thereto but the P-typeand N-type metal bumpers 170 and 180 may be formed on the P-regions Aand the N-regions B, respectively. At this time, certain metalelectrodes (not shown) may be further formed on the N-type and P-typesemiconductor layers 130 and 150 so as to be bonded to the metal bumpers170 and 180.

FIGS. 6 and 7 are circuit diagrams illustrating arrays of light emittingcells is according to embodiments of the present invention.

Referring to FIG. 6, a first serial array 31 is formed by coupling lightemitting cells 31 a, 31 b and 31 c in series, and a second serial array33 is formed by coupling other light emitting cells 33 a, 33 b and 33 cin series. Here, the term “serial array” refers to an array of aplurality of light emitting cells coupled in series.

Both ends of each of the first and second serial arrays 31 and 33 areconnected to an AC power source 35 and a ground, respectively. The firstand second serial arrays are connected in reverse parallel between theAC power source 35 and the ground. That is, both ends of the firstserial array are electrically connected to those of the second serialarray, and the first and second serial arrays 31 and 33 are arrangedsuch that their light emitting cells are driven by currents flowing inopposite directions. In other words, as shown in the figure, anodes andcathodes of the light emitting cells included in the first serial array31 and anodes and cathodes of the light emitting cells included in thesecond array 33 are arranged in opposite directions.

Thus, if the AC power source 35 is in a positive phase, the lightemitting cells included in the first serial array 31 are turned on toemit light, and the light emitting cells included in the second serialarray 33 are turned off. On the contrary, if the AC power source 35 isin a negative phase, the light emitting cells included in the firstserial array 31 are turned off, and the light emitting cells included inthe second serial array 33 are turned on.

Consequently, the first and second serial arrays 31 and 33 arealternately turned on/off by the AC power source so that the lightemitting chip including the first and second serial arrays can continueto emit light.

Although LED chips each of which comprises a single LED can be connectedto one another to be driven by an AC power source as in the circuit ofFIG. 6, space occupied by is the LED chips are increased. However, inthe LED chip of the present invention, a single chip can be driven bybeing connected to an AC power source, thereby preventing an increase inspace occupied by the LED chip.

Meanwhile, although the circuit shown in FIG. 6 is configured such thatthe both ends of each of the first and second serial arrays areconnected to the AC power source 35 and the ground, respectively, thecircuit may be configured such that the both ends thereof are connectedto both terminals of the AC power source. Further, although each of thefirst and second serial arrays comprises three light emitting cells,this is only an illustrative example for better understanding and thenumber of light emitting cells may be increased, if necessary. Thenumber of serial arrays may also be increased.

Referring to FIG. 7, a serial array 41 comprises light emitting cells 41a, 41 b, 41 c, 41 e and 41 f. Meanwhile, a bridge rectifier includingdiode cells D1, D2, D3 and D4 is arranged between an AC power source 45and the serial array 41, and between a ground and the serial array 41.Although the diode cells D1, D2, D3 and D4 may have the same structureas the light emitting cells, they are not limited thereto but may notemit light. An anode terminal of the serial array 41 is connected to anode between the diode cells D1 and D2, and a cathode terminal thereofis connected to a node between the diode cells D3 and D4. Meanwhile, aterminal of the AC power source 45 is connected to a node between thediode cells D1 and D4, and the ground is connected to a node between thediode cells D2 and D3.

If the AC power source 45 is in a positive phase, the diode cells D1 andD3 of the bridge rectifier are turned on, and the diode cells D2 and D4thereof are turned off. Therefore, current flows to the ground via thediode cell D1 of the bridge rectifier, the serial array 41 and the diodecell D3 thereof.

Meanwhile, if the AC power source 45 is in a negative phase, the diodecells D1 and D3 of the bridge rectifier are turned off, and the diodecells D2 and D4 thereof are turned on. Therefore, current flows to theAC power source via the diode cell D2 of the bridge rectifier, theserial array 41 and the diode cell D4 thereof.

Consequently, the bridge rectifier is connected to the serial array 41so that the serial array 41 can be continuously driven using the ACpower source 45. Here, although the bridge rectifier is configured suchthat the terminals of the bridge rectifier are connected to the AC powersource 45 and the ground, the bridge rectifier may be configured suchthat the both terminals are connected to both terminals of an AC powersource. Meanwhile, as the serial array 41 is driven using the AC powersource, a ripple may occur, and an RC filter (not shown) may beconnected to prevent the occurrence of a ripple.

According to this embodiment, a single serial array may be driven bybeing electrically connected to an AC power source, and the lightemitting cells can be effectively used as compared with the LED chip ofFIG. 6.

LED packages or LED lamps with various structures may be provided bymounting an LED chip with the array of light emitting cells coupled inseries or a submount having light emitting cells bonded thereto. LEDpackages or LED lamps with the array of light emitting cells coupled inseries will be described in detail below.

FIGS. 8 to 10 are sectional views illustrating LED packages according toembodiments of the present invention.

Referring to FIG. 8, the LED package comprises a substrate 310,electrodes 320 and 325 formed on the substrate 310, a light emittingdevice 350 mounted on the substrate 310 and a molding member 370encapsulating the light emitting device 350.

The light emitting device 350 comprises an array of light emitting cellscoupled in series through wires 80 as described with reference to FIGS.1 and 2, or comprises a submount 2000 with the electrode patterns 250and an array of light emitting cells coupled in series through theelectrode patterns of the submount 2000 as described with reference toFIGS. 3 to 5. The light emitting device 350 comprises at least one arrayof light emitting cells, and may comprise at least two arrays of lightemitting cells coupled in reverse parallel and/or an additionalrectification bridge unit for a predetermined rectification operation.

Each of the light emitting cells comprises an N-type semiconductor layerand a P-type semiconductor layer, and the N-type semiconductor layer ofone light emitting cell and the P-type semiconductor layer of anotherlight emitting cell adjacent thereto are electrically connected to eachother. Meanwhile, an N-type bonding pad and a P-type bonding pad may beformed to connect an external power source to one end and the other endof the array of light emitting cells coupled in series. In additionthereto, power source pads may be formed in the rectification bridgeunit in a case where the light emitting device 350 includes theadditional rectification bridge unit.

Since the light emitting cells are formed on a single substrate, it ispossible to simplify a fabricating process and to reduce the size of apackage as compared with a prior art in which respective light emittingdiodes are mounted and then coupled in series.

The substrate 310 may be a printed circuit board with first and secondlead electrodes 320 and 325 printed thereon. The lead electrodes 320 and325 are electrically connected to the P-type bonding pad (90 in FIGS. 1and 2, or 240 in FIGS. 3 to 5) and the N-type bonding pad (95 in FIGS. 1and 2, or 250 in FIGS. 3 to 5), or the power source pads of the lightemitting device 350, respectively.

The lead electrodes 320 and 325 may be formed using a printing techniqueor attached to the substrate 310 using an adhesive. The first and secondelectrodes 320 and 325 may be made of a metallic material containingcopper or aluminum with superior conductivity and formed such that theyare electrically separated from each other.

The lead electrodes 320 and 325, and the light emitting device 350 areelectrically connected to one another through bonding wires 390. Thatis, the first electrode 320 and one pad of the light emitting device 350are connected through one bonding wire 390, and the second electrode 325and the other pad of the light emitting device 350 are connected throughanother bonding wire 390.

The molding member 370 may be formed by curing a thermosetting resin,e.g., an epoxy or silicone resin. The molding member 370 may be formedin various forms such as a lens, a hexahedron, a flat plate, ahemisphere or a cylinder and further include a plurality of small lensfeatures on the top surface thereof.

Meanwhile, the LED package may further comprise a predetermined phosphor(not shown) for realizing light of a target color over the lightemitting device 350. The phosphor may be applied on the light emittingdevice 350. Further, after the phosphor and the thermosetting resin aremixed together, the molding member 370 is formed using the mixture sothat the phosphor can be dispersed in the molding member 370.

The LED package according to this embodiment may further comprise areflective portion. FIGS. 9 and 10 show LED packages with such areflective portion.

Referring to FIG. 9, the light emitting device 350 is mounted within areflective portion 340. The reflective portion 340 may be formed bymechanically processing the substrate (310 in FIG. 8) to form apredetermined groove. An inner wall of the groove is formed to have acertain slope. As a result, light emitted from the light emitting device350 and then incident on the reflective portion 340 is reflected fromthe reflective portion 340 to the outside so that luminance of the lightcan be improved. It is preferred that a bottom surface of the groove isin the form of a plane to mount the light emitting device 350 thereon.

Referring to FIG. 10, a reflective portion 360 is formed on a flatsubstrate 310 to surround a light emitting device 350. The reflectiveportion 360 has a certain slope to reflect light, which is incident fromthe light emitting device 350, to the outside. The reflective portion360 may be formed by molding a thermoplastic or thermosetting resin.Meanwhile, a molding member 370 encapsulates the light emitting device350 by filling the inside of the reflective portion 360.

Further, the reflective portion 360 and the substrate 310 may be formedintegrally with each other. At this time, lead electrodes 320 and 325are formed using a lead frame, and the reflective portion 360 and thesubstrate 310 are formed by insert-molding the lead frame.

The LED packages according to embodiments of the present invention maycomprise one or more light emitting devices 350 as described above. FIG.11 is a sectional view illustrating an LED package having a plurality oflight emitting devices 350.

Referring to FIG. 11, the LED package according to this embodimentcomprises a substrate 310, lead electrodes 320 and 325 formed on thesubstrate 310, and a plurality of light emitting devices 350 mounted onthe substrate 310. To enhance luminance of light, a reflective portion360 is formed to surround the light emitting devices 350, and a moldingmember 370 encapsulating the light emitting devices 350 is formed overthe light emitting devices 350. Further, the lead electrodes 320 and 325are formed on the substrate 350 and connected to the plurality of lightemitting devices 350 through bonding wires 390. Accordingly, theplurality of is light emitting devices 350 can be connected to anexternal power source through the lead electrodes 320 and 325 and thebonding wires 390.

As described with reference to FIG. 8, each of the light emittingdevices 350 comprises an array of light emitting cells coupled inseries.

According to this embodiment, the plurality of light emitting devices350 are variously mounted in series, parallel or series-parallel on thesubstrate 310 to obtain desired luminous power, and high luminous powercan be obtained by mounting the plurality of light emitting devices 350.

FIGS. 12 and 13 are sectional views illustrating LED packages each ofwhich employs a heat sink according to some embodiments of the presentinvention.

Referring to FIG. 12, the LED package according to this embodimentcomprises a substrate or housing 311, which is formed with leadelectrodes 320 and 325 at both sides thereof and also has athrough-hole, a heat sink 313 mounted inside the through-hole of thehousing 311, a light emitting device 350 mounted on the heat sink 313,and a molding member 370 encapsulating the light emitting device 350.

The heat sink 313 mounted inside the through-hole of the housing 311 ismade of a material with superior thermal conductivity and dissipatesheat generated from the light emitting device 350 to the outside. Asshown in FIG. 13, the heat sink 313 may have a recessed region of aninverted frusto-conial shape in a predetermined region of the centerthereof. The recessed region constitutes a reflective portion 380, andthe light emitting device 350 is mounted on a bottom surface of therecessed region. To enhance luminance and light-focusing performance,the recessed region of the inverted frusto-conial shape is formed tohave a certain slope.

As described with reference to FIG. 8, the light emitting device 350comprises an array of light emitting cells coupled in series. The lightemitting device 350 is connected to the lead electrodes 320 and 325through bonding wires 390. Further, in these embodiments, a plurality oflight emitting devices 350 may be mounted on the heat sink 313.

As described with reference to FIG. 8, the molding member 370encapsulating the light emitting device 350 may be formed in variousshapes. Further, a phosphor (not shown) is formed over the lightemitting device 350 to emit light of a target color.

FIGS. 14 to 17 are views illustrating LED packages each of which employsa heat sink according to other embodiments of the present invention.FIGS. 14 and 15 are perspective and plan views illustrating an LEDpackage 410 according to an embodiment of the present invention,respectively, and FIG. 16 is a plan view illustrating lead frames 415and 416 used in the LED package 410. Meanwhile, FIG. 17 is a sectionalview illustrating the LED package.

Referring to FIGS. 14 to 17, the LED package 410 comprises a pair oflead frames 415 and 416, a heat sink 413 and a package body 411supporting the lead frames and the heat sink.

As shown in FIG. 17, the heat sink 413 may have a base and a protrusionprotruding upwardly from a central portion of the base. Although thebase and the protrusion can have cylindrical shapes as shown in thefigure, they are not limited thereto but may have various forms such asa polygonal post and combinations thereof. Meanwhile, an externalappearance of the package body 411 may be modified depending on theshape of the base of the heat sink 413. For example, in a case where thebase is in the form of a cylinder, the external appearance of thepackage body 411 may be a cylinder as shown in the figure.Alternatively, in a case where the base is in the form of a rectangularpost, the external appearance of the package is body 411 may be arectangular post.

The heat sink 413 has a lead frame-receiving groove 413 a for receivingthe lead frame 415 at a side surface of the protrusion. Although thereceiving groove 413 a can be formed at a portion of the side surface ofthe protrusion, it may be preferably formed as a continuous groove alongthe side surface of the protrusion. Accordingly, it is easy to combinethe lead frame 415 into the continuous receiving groove 413 a regardlessof rotation of the heat sink 413.

Meanwhile, the heat sink 413 may have a latching groove at a sidesurface 413 b of the base. The latching groove may be formed at aportion of the side surface 413 b of the base, or it may be continuousalong the surface thereof. Since heat dissipation is promoted as abottom surface of the heat sink 413 becomes broader, a lower end portionof the side surface of the base may be exposed to the outside as shownin FIGS. 14 and 17. However, the latching groove and a portion of theside surface of the base above the latching groove are covered with thepackage body 411. Thus, the latching groove receives a portion of thepackage body 411, so that the heat sink 413 can be prevented from beingseparated from the package body 411.

The heat sink 413 is made of a conductive material, particularly, ametal such as copper (Cu) or aluminum (Al), or an alloy thereof.Further, the heat sink 413 may be formed using a molding or pressingtechnique.

The pair of lead frames 415 and 416 are located around the heat sink 413while being spaced apart from each other. The lead frames 415 and 416have inner lead frames 415 a and 416 a, and outer lead terminals 415 band 416 b, respectively. The inner lead frames 415 a and 416 a arelocated inside the package body 411, and the outer lead frames 415 b and416 b extend from the inner lead frames and protrude toward the outsideof the package body 411. At this time, the outer lead frames 415 b and416 b may be bent for surface mounting.

Meanwhile, the inner lead frame 415 a is combined into the receivinggroove 413 a of the heat sink 413 and then electrically connecteddirectly to the heat sink. As shown in FIG. 16, the inner lead frame 415a may take the shape of a ring of which a portion is removed to bereceived in the receiving groove 413 a of the heat sink 413. As theportion removed from the ring-shaped inner lead frame becomes smaller, acontact surface between the heat sink 413 and the inner lead frame 415 amore increases to reinforce electrical connection. At this time, theinner lead frame 415 a may take various shapes such as a circular ringor a polygonal ring depending on the shape of the protrusion of the heatsink 413.

On the other hand, the inner lead frame 416 a is located while beingspaced apart from the heat sink 413. The inner lead frame 416 a islocated at the removed portion of the inner lead frame 415 a so that itcan be located close to the heat sink 413. The lead frame 416 may have afastening groove 416 c, and the fastening groove 416 c receives aportion of the package body 411 so that the lead frame 416 can beprevented from being separated from the package body 411. The lead frame415 may also have a fastening groove.

The package body 411 supports the heat sink 413 and the lead frames 415and 416. The package body 411 may be formed using an insert-moldingtechnique. That is, the package body 411 may be formed by combining thelead frame 415 into the receiving groove of the heat sink 413,positioning the lead frame 416 at a corresponding position, andinsert-molding a thermoplastic or thermosetting resin. Using theinsert-molding technique, the package body 411 of such a complicatedstructure can be easily formed. At this time, the protrusion of the heatsink 413 may protrude upwardly beyond the top of the package body 411.

Meanwhile, the package body 411 has an opening for exposing portions ofthe respective inner lead frames 415 a and 416 a, and a portion of theprotrusion of the heat sink 413. Thus, a groove is formed between theprotrusion of the heat sink 413 and the package body 411. As shown inFIGS. 14 and 15, although the groove may be a continuous groove alongthe periphery of the protrusion, it is not limited thereto but may beintermittent.

Further, the package body 411 may further comprise an encapsulantreceiving groove 411 a located along the outer periphery thereof. Theencapsulant receiving groove 411 a receives a molding member orencapsulant 421 so that the encapsulant 421 is prevented from beingseparated from the package body 411. In addition thereto, a marker 411 bfor indicating the positions of the lead frames 415 and 416 may beformed at the package body as shown in FIGS. 14 and 15. The marker 411 bindicates the position of the lead frame 415 directly connected to theheat sink 413 and the position of the lead frame 416 spaced apart fromthe heat sink.

Since the package body 411 is formed using the insert-molding technique,it fills the latching groove formed at the side surface 413 b of thebase of the heat sink 413, thereby supporting the heat sink. In additionthereto, the lead frame 415 is received in the receiving groove 413 a ofthe heat sink, and the lead frame is also supported by the package body.Further, the package body fills the remainder of the receiving groove413 a except the portion thereof contacted with the lead frame. Thus,according to the embodiments of the present invention, the heat sink isprevented from being separated from the package body.

Referring again to FIG. 17, a light emitting device 417 is mounted onthe heat sink 413. The light emitting device 417 comprises an array oflight emitting cells coupled in series through bonding wires 80 asdescribed with reference to FIGS. 1 and 2, or comprises a submount 2000with electrode patterns 250 and an array of light emitting cells coupledin series through the electrode patterns 250 of the submount 2000. Thelight emitting device 417 may comprise at least one array of lightemitting cells, and may comprise at least two arrays of light isemitting cells connected in reverse parallel and/or an additionalrectification bridge unit for a predetermined rectification operation.

The light emitting device 417 is electrically connected to the leadframes 415 and 416 through bonding wires 419 a and 419 b. For example,in a case where the light emitting device 417 is an LED chip describedwith reference to FIG. 1 or 2, the bonding wires 419 a and 419 b connectthe bonding pads (90 and 95 of FIG. 1 or 2) formed at both ends of thearray of light emitting cells coupled in series to the lead frames 415and 416.

Further, in a case where the light emitting device 417 comprises thesubmount 2000 and the light emitting cells 100 bonded on the submount asdescribed with reference to FIGS. 3 to 5, the bonding wires 419 a and419 b connect the bonding pads 240 and 250 formed on the submount to thelead frames 415 and 416. If the LED chip 1000 is bonded to the submount2000 as shown in FIG. 3 or 5, the submount 2000 is interposed betweenthe LED chip 1000 and the heat sink 413.

The bonding wire 419 b may be connected directly to the lead frame 415or the heat sink 413.

Meanwhile, the encapsulant 421 covers the top of the LED chip 417. Theencapsulant 421 may be an epoxy or silicone resin. Further, theencapsulant may contain a phosphor 421 a for converting the wavelengthof light emitted from the LED chip 417. For example, in a case where theLED chip 417 emits blue light, the encapsulant 421 may contain thephosphor 421 a for converting the blue light into yellow light, or greenand red light. As a result, white light is emitted from the LED packageto the outside.

The encapsulant 421 fills the opening of the package body 411 and theencapsulant receiving groove 411 a. Therefore, the bonding force of theencapsulant 421 with the is package body 411 increases so that theencapsulant is prevented from being separated from the LED package.Meanwhile, the encapsulant 421 may be a lens and take the shape of aconvex lens such that light emitted from the LED chip 417 emerges in apredetermined range of directional angles as shown in FIG. 17.Otherwise, the encapsulant may have various shapes depending on theobject of use thereof.

FIG. 18 is a sectional view illustrating an LED package employing a heatsink according to a further embodiment of the present invention.

Referring to FIG. 18, the LED package according to this embodimentcomprises a pair of lead frames 415 and 416, a heat sink 413 and apackage body 411. Further, as described with reference to FIG. 17, alight emitting device 417 is mounted on the heat sink 413, bonding wires419 a and 419 b connect the light emitting device 417 to the lead frames415 and 416, and an encapsulant 421 covers the top of the LED chip 417.A phosphor 421 a may be contained within the encapsulant 421. Featuresthereof different from the LED package of FIG. 17 will be describedbelow.

In the LED package according to this embodiment, the heat sink 413 andthe lead frame 415 are formed integrally with each other. That is, thelead frame 415 is made of the same material as the heat sink 413, andformed together with the heat sink 413. Since the heat sink 413 and thelead frame 415 are formed integrally with each other, the receivinggroove (413 a of FIG. 17) for the lead frame can be eliminated.

According to this embodiment, since the heat sink 413 and the lead frame415 are formed integrally with each other, the heat sink 413 can be moreprevented from being separated from the package body 411.

FIGS. 19 to 23 are views illustrating LED packages each of which employsa heat is sink according to further embodiments of the presentinvention. Here, FIGS. 19 and 20 are upper and lower perspective viewsillustrating an LED package according to an embodiment of the presentinvention, and FIG. 21 is an exploded perspective view illustrating theLED package. Meanwhile, FIG. 22 is a sectional view showing that an LEDchip is mounted on the LED package of FIGS. 19 and 20 and connectedthereto through bonding wires, and FIG. 23 is a sectional view showingthat a molding member is formed on an LED package of FIG. 22 and a lensis mounted thereon.

Referring to FIGS. 19 to 21, the LED package of the present inventioncomprises a package body including a first package body 506 and a secondpackage body 509. Although the first package body and the second packagebody may be separately fabricated, they may be formed integrally witheach other using an insert-molding technique. If they are formedintegrally with each other, they are not separated into the firstpackage body 506 and the second package body 509. For the sake ofconvenience of description, however, they are shown in a separatedstate.

The first package body 506 has an opening 508 and is formed at an upperface thereof with a groove that is recessed to receive an encapsulant ora molding member and surrounded by an inner surface thereof. Althoughthe opening 508 has the same area as the recessed portion, it may havean area smaller than that of the recessed portion as shown in thefigure. A stepped portion 507 may be formed in the inner wall of thefirst package body to receive the molding member that will be describedlater. The second package body 509 has a through-hole 511 exposedthrough the opening of the first package body 506. Further, innerframe-receiving grooves 510 are formed in an upper face of the secondpackage body 509, and a heat sink-seating groove 512 is formed in alower face thereof. The inner frame-receiving is grooves 510 are locatedaround the through-hole 511 while being spaced apart therefrom.

A pair of lead frames 501 are located between the first package body 506and the second package body 507 while being spaced apart from eachother. The lead frames 501 have a pair of inner frames 503 exposedthrough the opening of the first package body 506, and outer frames 503extending from the inner frames and protruding to the outside of thepackage body. The inner frames 503 are arranged to form a symmetricstructure so that a hollow portion 505 can be defined at a centralposition therebetween. The inner frames 503 are seated inside the innerframe-receiving grooves 510 such that the through-hole 511 is locatedinside the hollow portion 505.

Meanwhile, each of the inner frames 503 may have supports 504 extendingtherefrom. The supports 504 function to support the lead frames 501 whena lead panel (not shown) having a plurality of lead frames 501 connectedthereto is used for mass-production of LED packages. Further, as shownin FIGS. 19 and 20, the outer frames 502 may be bent such that the LEDpackage can be mounted on the surface of a printed circuit board or thelike.

Meanwhile, the lead frames 501 can form a symmetric structure as shownin the figure but is not limited thereto. Moreover, although the hollowportion 505 surrounded by the inner frames may have a hexagonal shape,it is not limited thereto but may have various shapes such as a circle,a rectangle and the like.

The heat sink 513 is combined with the second package body 509 on thelower face of the second package body 509. The heat sink 513 has a base514 seated in the heat sink-seating groove 512 of the second packagebody, and a protrusion 515 to be combined with the second package bodywhile protruding at a central portion of the base and to be insertedinto the through-hole 511 of the second package body. A latching stepmay be formed on a side surface is of the protrusion 515. An uppersurface 516 of the protrusion 515 may be recessed and exposed throughthe opening 508 of the first package body 506.

Meanwhile, the first and second package bodies 506 and 509 can be madeof materials such as thermal conductive plastics or high thermalconductive ceramics. The thermal conductive plastics includeacrylonitrile butadiene styrene (ABS), liquid crystalline polymer (LCP),polyamide (PA), polyphenylene sulfide (PPS), thermoplastic elastomer(TPE) and the like. The high thermal conductive ceramics include alumina(Al₂O₃), silicon carbide (SiC), aluminum nitride (AlN) and the like.Among the ceramics, aluminum nitride (AlN) has properties equivalent tothose of alumina and is superior to alumina in view of thermalconductivity. Thus, aluminum nitride has been widely used in practice.

If the first and second package bodies 506 and 509 are made of thermalconductive plastics, they may be formed using an insert-moldingtechnique after the lead frames 501 are located therebetween.

On the other hand, if the first and second package bodies 506 and 509are made of the high thermal conductive ceramics, the first package body506 and the second package body 509 may be separately formed and thenfixedly attached thereto using an adhesive with strong adhesive force orthe like.

Referring to FIG. 22, in the LED package according to the presentinvention, two stepped portions 507 are formed in the inner wall of thefirst package body 506, so that they can serve as fixing steps for usein molding the molding member or in mounting a lens, which will bedescribed later.

Meanwhile, a latching step 515 a of the heat sink 513 is formed at anside surface of the protrusion 515 so that it can be fixedly insertedinto a groove formed in a wall defining the through-hole 511 of thesecond package body 509. Further, the latching step 515 a may be formedat an upper portion of the protrusion 515 to be coupled to the upperface of the second package body 509. Accordingly, the heat sink 513 canbe prevented from being separated from the package body. The latchingstep 515 a may be formed on a side surface of the base.

The heat sink 513 is made of a thermally conductive material,particularly, a metal such as copper (Cu) or aluminum (Al), or an alloythereof. Further, the heat sink 513 may be formed using a molding orpressing technique.

The light emitting device 517 is mounted on the upper surface 516 of theheat sink 513. Since the light emitting device 517 is the same as thelight emitting device 417 described with reference to FIG. 17, adescription thereof will be omitted.

Referring to FIG. 23, molding members 521 and 523 encapsulate the top ofthe light emitting device 517 and are molded inside the groove of thefirst package body 506. The molding member can comprise the firstmolding member 521 and the second molding member 523. Each of the firstand second molding members may be made of an epoxy or silicone resin,and they may be made of the same material or different materials. It ispreferred that the second molding member 523 have a value of hardnesslarger than that of the first molding member 521. The first and secondmolding members can fill the groove of the first package body 506 toform an interface in the vicinity of the stepped portions 507 a.

Meanwhile, a phosphor may be contained in the first molding member 521and/or the second molding member 523. Further, a diffuser for diffusinglight may be contained in the first molding member 521 and/or the secondmolding member 523. The phosphor is applied on the light emitting device517 so that it may be disposed between the first molding member 521 andthe light emitting device 517, or on the first molding member 521 or thesecond molding is member 523.

Further, a lens 525 may be disposed on the top of the molding member.The lens 525 is fixed to an upper one of the stepped portions 507 b. Thelens 525 take the shape of a convex lens such that light emitted fromthe LED chip 517 emerges in a predetermined range of directional anglesas shown in the figure. Otherwise, the lens may have various shapesdepending on the object of use thereof.

FIG. 24 is a sectional view illustrating an LED lamp having lightemitting cells coupled in series according to an embodiment of thepresent invention.

Referring to FIG. 24, the LED lamp comprises a top portion 603, and afirst lead with a pin-type leg 601 a extending from the top portion 603.A second lead with a pin-type leg 601 b is arranged to correspond to thefirst lead while being spaced apart from the first lead.

The light emitting device 617 is mounted on the top portion 603 of thefirst lead. The top portion 603 of the first lead may have a recessedcavity, and the light emitting device 617 is mounted inside the cavity.A sidewall of the cavity may form an inclined reflective surface suchthat light emitted from the light emitting device 617 can be reflectedin a predetermined direction. The light emitting device 617 iselectrically connected to the first and second leads through bondingwires 613 a and 613 b.

Since the light emitting device 617 is the same as the light emittingdevice 417 described with reference to FIG. 17, a description thereofwill be omitted.

Meanwhile, a molding member 611 encapsulates the top portion 603 of thefirst lead, the light emitting device 617, and a portion of the secondlead. The molding member 611 is generally formed of a transparent resin.The molding member 611 may protect the light emitting device 617 andsimultaneously have a lens function of refracting light, which has beenis emitted from the LED chip 617, in a range of predetermineddirectional angles.

In addition thereto, an encapsulant 609 is formed inside the cavity tocover the top of the light emitting device 617. The encapsulant 609 maybe made of an epoxy or silicone resin.

Meanwhile, the encapsulant 609 may contain a phosphor. The phosphorconverts the wavelength of light emitted from the light emitting device617 so that light with a desired wavelength can be emitted. The phosphormay be formed by being applied on the light emitting device 617.

The pin-type legs 601 a and 601 b are inserted through and mounted on aprinted circuit board (PCB) (not shown), and a current is applied to theLED lamp through the PCB so that the light emitting device 617 can emitlight. Meanwhile, the pin-type legs 601 a and 601 b may be directlyconnected to a socket of a household AC power source. Thus, the LED lampcan be used for general illumination at home.

Next, high flux LED lamps, which are a kind of LED lamp, according toother embodiments of the present invention will be described withreference to FIGS. 25 to 32.

FIGS. 25 and 26 are perspective views illustrating high flux LED lampsaccording to other embodiments of the present invention, and FIG. 27 isa sectional view of FIG. 26.

Referring to FIGS. 25 to 27, the high flux light emitting diode (LED)lamp has a first lead and a second lead. The first lead has a topportion 703. Two pin-type legs 701 a and 701 c extend from the topportion 703 and are exposed to the outside. The second lead has twopin-type legs 701 b and 701 d corresponding to the first lead, and thetwo pin-type legs 701 b and 701 d are connected to each other at upperportions thereof. The first and second leads may be made of a metal suchas copper or iron, or an alloy thereof, and they may be formed using ais molding technique.

The top portion 703 of the first lead has an upper surface oil which alight emitting device 717 is to be mounted, and a lower surface. Theupper surface of the top portion 703 may be a flat surface. Further, asshown in FIG. 27, a cavity may be formed in the upper surface of the topportion 703, and the light emitting device 717 is mounted inside thecavity. A sidewall of the cavity may form an inclined reflective surfacesuch that light emitted from the LED can be reflected in a predetermineddirection.

Since the light emitting device 717 is the same as the light emittingdevice 417 described with reference to FIG. 17, a description thereofwill be omitted. The light emitting device 717 is electrically connectedto the first and second leads through bonding wires 713 a and 713 b.

Meanwhile, molding member 711 encapsulates the top portion 703 of thefirst lead, the light emitting device 717 and a portion of the secondlead. Although the molding member 711 may be formed of a transparentresin such as an epoxy or silicone resin, it may be formed of atranslucent resin depending on the object thereof. The molding member711 may protect the light emitting device 717 and simultaneously have alens function of refracting light, which has been emitted from the LEDchip 717, in a predetermined range of directional angles. Thus, anexternal appearance of the molding member 711 may take various shapesdepending on a desired directional angle. For example, an upper portionof the molding member 711 may be convex with a smaller curvature toobtain a narrow range of directional angles, whereas the upper portionof the molding member 711 may be substantially flat with a largercurvature to obtain a wide range of directional angles. Further, asshown in FIG. 25, the molding member 711 may be formed such that a lens711 a is defined in the vicinity of the upper portion of the is lightemitting device 717. Alternatively, as shown in FIG. 26, the moldingmember 711 may be formed such that the entire upper portion thereoftakes the shape of a lens.

In addition thereto, an encapsulant 709 may be formed inside the cavityto cover the top of the light emitting device 717. The encapsulant 709may be made of an epoxy or silicone resin. Meanwhile, the encapsulant709 may contain a phosphor as described with reference to FIG. 24.

The pin-type legs 701 a, 701 b, 701 c and 701 d are inserted through andmounted on a printed circuit board (PCB) (not shown), and may be thenfixed by means of soldering. A current is applied to the LED lampthrough the PCB so that the light emitting device can emit light.

FIG. 28 is a perspective view illustrating a high flux LED lampaccording to a further embodiment of the present invention, and FIGS. 29and 30 are sectional and side views of FIG. 28, respectively.

Referring to FIGS. 28 to 30, the LED lamp comprises a top portion 723and a first lead with a snap-type leg 721 a extending from the topportion 723. The snap-type leg 721 a has a wide side surface and a bentportion 722 a that is bent substantially perpendicularly at a lowerportion thereof. Further, a second lead with a snap-type leg 721 b isarranged to correspond to the first lead while being spaced aparttherefrom. The snap type leg 721 b of the second lead also has a wideside surface and a bent portion 722 b that is bent substantiallyperpendicularly at a lower portion thereof. It is preferred that thebent portions 722 a and 722 b extend in opposite directions. The firstand second leads may be made of a metal such as copper or iron, or analloy thereof, and they may be formed using a molding technique.

As described with reference to FIG. 27, the top portion 723 of the firstlead has an is upper surface on which a light emitting device 717 is tobe mounted and a lower surface. The upper surface of the top portion 723may be a flat surface. Alternatively, as shown in FIG. 29, a cavity maybe formed in the upper surface of the top portion 723, and the lightemitting device 717 is mounted inside the cavity. A sidewall of thecavity may form an inclined reflective surface such that light emittedfrom the LED can be reflected in a predetermined direction.

As described with reference to FIG. 27, the light emitting device 717 iselectrically connected to the first and second leads through bondingwires 713 a and 713 b. Thus, after the bent portions 722 a and 722 b ofthe first and second leads are fixed to the PCB, a current is applied tothe LED lamp through the PCB.

Meanwhile, as described above, the molding member 711 encapsulates thetop portion 723 of the first lead, the light emitting device 717 and aportion of the second lead, and an encapsulant 709 can cover the lightemitting device 717 inside the cavity. Further, the encapsulant 709 maycontain a phosphor.

Meanwhile, a heat sink 723 a may extend from the top portion 723 of thefirst lead in a direction parallel with the leg 721 a of the first lead.The heat sink 723 a protrudes at least outside the molding member 711.The heat sink 723 a may extend to the lowermost portion of the leg 721 aof the first lead. Accordingly, in a case where the LED lamp is mountedon the PCB, the heat sink 723 a may also be attached to the PCB. Theheat sink 723 a may have grooves on the surface thereof. The groovesincrease the surface area of the heat sink 723 a. Such grooves may beformed to have various shapes and widths. The heat sink 723 a may beformed integrally with the top portion 723 and leg 721 a of the firstlead.

According to the embodiments of the present invention, the LED chip 717emits light by means of the current applied thereto and also generatesheat at this time. The heat is generated from the LED chip 717 isdissipated to the outside via the top portion 723 and leg 721 a of thefirst lead, the second lead and the wires 713 a and 713 b. Since thelegs 721 a and 721 b of the first and second leads are of a snap type,the surface area thereof is broader than those of the pin-type legs.Thus, the heat dissipation performance of the LED lamp is enhanced. Inaddition thereto, in a case where the heat sink 723 a extends from thetop portion 723 of the first lead, heat can be dissipated through theheat sink 723 a, so that the heat dissipation performance of the LEDlamp can be more enhanced. The heat sink 723 a may extend from the topportion 703 of the high flux LED lamp with the pin-type legs 701 a to701 d described with reference to FIGS. 25 to 27.

FIGS. 31 and 32 are side views illustrating high flux LED lamps in whichheat dissipation performance is enhanced by modifying the snap-type legs721 a and 721 b.

Referring to FIG. 31, although the LED lamp has the same components asthe LED lamp described with reference to FIGS. 28 to 30, it has asnap-type leg 751 a of a first lead and/or a snap-type leg (not shown)of a second lead, which are modified from the snap-type legs 721 a and721 b of the first lead and/or the second lead. That is, the leg 751 aof the first lead has at least one through-hole 751 h through which aircan pass. Further, the leg of the second lead may also have at least onethrough-hole through which air can pass. The through-holes 751 h may beformed to take various shapes such as a rectangle, a circle, and anellipse. Moreover, the through-holes 751 h may be arranged in variouspatterns within the leg 751 a of the first lead. That is, as shown inFIG. 31, the through-holes may be arranged in rows, in columns, or in amatrix. The through-holes 751 h may also be arranged within the leg ofthe second lead.

According to this embodiment, since air can pass through thethrough-holes 751 h, the legs of the leads can be cooled by means ofconvection. Thus, the heat dissipation performance of the LED lamp canbe more enhanced.

Referring to FIG. 32, although the LED lamp according to this embodimenthas the same components as the LED lamp described with reference toFIGS. 28 to 30, it has a snap-type leg 771 a of a first lead and/or asnap-type leg (not shown) of a second lead, which are modified from thesnap-type legs 721 a and 721 b of the first lead and/or the second lead.That is, the leg 771 a of the first lead has grooves 771 g. The grooves771 g may be formed on an outer surface and/or an inner surface of theleg 771 a of the first lead. Further, the grooves 771 g may be formed onthe leg of the second lead. The grooves 771 g may be formed to takevarious shapes such as a line and a spiral.

According to this embodiment, the surface area of the leg of the firstlead and/or that of the second lead can be increased, thereby moreenhancing heat dissipation performance through the leg of the first leadand/or the leg of the second lead.

What is claimed is:
 1. A light emitting diode (LED) package, comprising: a heat sink; an LED chip arranged on a chip mounting portion of the heat sink; at least two lead frames spaced apart from the heat sink; and a package body coupled with the heat sink and the at least two lead frames, wherein the chip mounting portion of the heat sink and at least a portion of the at least two lead frames are exposed from a top side of the package body, and a base of the heat sink is exposed from a bottom side of the package body, wherein the heat sink comprises a protrusion, and the chip mounting portion is recessed below the protrusion, wherein the heat sink further comprises a latching step, and the latching step is arranged above the chip mounting portion, and wherein the latching step protrudes from a side surface of the protrusion.
 2. The LED package of claim 1, wherein the at least two lead frames are arranged on and spaced apart from an upper surface of the heat sink.
 3. The LED package of claim 1, wherein the latching step is configured to prevent the heat sink from being separated from the package body.
 4. The LED package of claim 1, wherein the latching step is arranged on a side surface of the heat sink protrusion.
 5. The LED package of claim 3, wherein the latching step is arranged on a side surface of the base of the heat sink.
 6. The LED package of claim 1, wherein each lead frame comprises an inner frame and an outer frame extending from the inner frame in a first direction and protruding to the outside of the package body.
 7. The LED package of claim 6, wherein each outer frame protrudes to the outside of the package body through a side surface of the package body.
 8. The LED package of claim 1, further comprising: a molding member arranged on a top portion of the LED chip.
 9. The LED package of claim 8, wherein the molding member comprises a first molding member adjacent to the LED chip and a second molding member spaced apart from the LED chip.
 10. The LED package of claim 9, wherein the second molding member has a hardness value larger than that of the first molding member.
 11. The LED package of claim 6, wherein the inner frames of the at least two lead frames are arranged to form a symmetric structure to define a hollow portion at a central position between the inner frames.
 12. The LED package of claim 6, wherein each lead frame further comprises a support extending from the inner frame in a second direction substantially perpendicular to the first direction.
 13. The LED package of claim 1, wherein a top surface of the protrusion and a top surface of the lead frames are coplanar.
 14. The LED package of claim 1, wherein the package body comprises a stepped portion.
 15. The LED package of claim 1, wherein the package body comprises a first package body and a second package body that is not integrally formed with the first package body.
 16. The LED package of claim 1, wherein the package body is integrally formed.
 17. The LED package of claim 1, wherein the latching step is inserted into a groove in the package body.
 18. The LED package of claim 15, wherein a first stepped portion and a second stepped portion are arranged in an inner wall of the first package body. 